Abstract
The increasing complexity of human-machine interaction and system monitoring require increased awareness of operator’s workload levels to increase safety and productivity in operational environments. Subjective workload scales are subject to operator biases, possible intrusiveness, and low temporal sensitivity. Physiological measures have recently been used because of their ability to bypass many of these limitations and provide more objective and sensitive measures of workload. Transcranial Doppler Sonography (TCD), for instance, is unobtrusive, has good temporal sensitivity, and is sensitive to workload effects on a variety of tasks, but is limited by its low spatial sensitivity. A new imaging measure, functional Tissue Pulsatility Imaging (fTPI), measures tissue velocity through ultrasound and provides similar temporal resolution but higher spatial resolution than TCD. This study explored the feasibility of using fTPI as a measure of mental workload. Participants performed 10 minute low and high event rate air traffic control vigilance tasks. The NASA-TLX was used to as a measure of subjective mental workload. Performance accuracy results reveal that task performance was worse in the high event rate task than in the low event rate task. Tissue velocity measured through fTPI showed significantly more tissue velocity in the right hemisphere, which is supported by previous TCD research. Further, fTPI results suggest that workload for the right hemisphere was higher for the high event rate task as compared to the low event rate task. The similarities between the tissue velocity results and previous TCD research support fTPI as a viable method for obtaining higher spatial resolution measures of mental workload.